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Southwest Climate Outlook October 2019 - Climate Summary

Wednesday, October 16, 2019

Monthly Precipitation and Temperature: September precipitation in Arizona ranged from much below average in the north, to much above average in the south, while most of New Mexico was average to below average (Fig. 1a). September temperatures were mostly average to much above average in Arizona and mostly much above average to record warmest in New Mexico (Fig. 1b). The daily average temperature anomalies for Sept 1 – Oct 15 (Fig. 2) highlight the fluctuations at select stations around the region.

 

 

Annual Precipitation and Temperature: Total precipitation for 2019 (Jan-Sept) in Arizona was mostly average to above average, with some below average in the four corners region, while New Mexico was drier with average to below average across most of the state, along with some pockets of much below average conditions (Fig. 3a). Mean temperatures in 2019 so far are mostly above average in Arizona and above average to much above average in New Mexico (Fig. 3b).

 

Drought: Water year precipitation (Oct 1 2018 – Sept 30 2019) was mostly normal to above normal across most of Arizona and much of northeastern New Mexico, while parts of eastern Arizona and south-central and northwestern New Mexico were normal to below normal (Fig. 4). These totals are buoyed by tropical storm activity in Oct 2018 and Sept 2019, and may be skewing some characterizations of longer term precipitation. Given recent conditions and the below average monsoon, drought has returned to much of Arizona and western New Mexico in the Oct 8 U.S. Drought Monitor (USDM) (Fig. 5). This designation is leaning more heavily on recent below average monsoon precipitation, despite water year precipitation totals.

 

 

Tropical Storm Activity: The eastern North Pacific hurricane season has been near normal, with 16 named storms as of Oct. 16 (Fig. 6), including four major hurricanes (category 4 or above), with the average through this date at approximately 15 named storms and 4 major hurricanes. The Accumulated Cyclonic Energy (ACE) to date is 95 (for comparison, last year this time ACE was 295), while the average to date is approximately 120. Recent notable events include heavy precipitation linked to TS Lorena and TS Mario, which funneled moisture into a cutoff low in mid-to-late September.  This brought highly variable but at times intense storms to southern Arizona, including some supercell formation in central and eastern Arizona. Given the meager monsoon, their impacts are visible on the percent of normal maps (see Monsoon Recap).

 

ENSO Update: Oceanic and atmospheric conditions are generally consistent with an ENSO-neutral outlook for 2019 and into 2020 (see ENSO-tracker for details).

Precipitation and Temperature Forecast: The three-month outlook for November through January calls for increased chances of above-normal precipitation in much of Arizona, New Mexico, and northwestern Mexico (Fig. 7, top). The three-month temperature outlook calls for increased chances of above-normal temperatures across the U.S. Southwest and northern Mexico (Fig. 7, bottom).

 

Online Resources

  • Figures 1,3 - National Centers for Environmental Information - ncei.noaa.gov
  • Figure 2 - Climate Assessment for the Southwest - climas.arizona.edu
  • Figure 4 - Western Regional Climate Center - wrcc.dri.edu
  • Figure 5 - U.S. Drought Monitor - droughtmonitor.unl.edu
  • Figure 7 - International Research Institute for Climate and Society - iri.columbia.edu

Southwest Climate Outlook - El Niño Tracker - October 2019

Wednesday, October 16, 2019

Forecast Roundup: Despite warmer waters in the equatorial Pacific, seasonal outlooks and forecasts based on sea surface temperature (SST) anomalies (Figs. 1-2) and other oceanic and atmospheric indicators, all point to ENSO-neutral conditions lasting through 2019 and into 2020. On Oct 10, the Japanese Meteorological Agency (JMA) highlighted lingering warmer-than-normal SSTs in the western equatorial Pacific, and maintained their call for a 60-percent chance of ENSO-neutral conditions to continue until winter 2019-2020. On Oct 10, the NOAA Climate Prediction Center (CPC) issued their ENSO diagnostic discussion with an inactive alert status, and focused on neutral conditions across the oceans and atmosphere. They called for an 85-percent chance of ENSO-neutral conditions persisting through fall 2019, and a 55- to 60-percent chance of ENSO-neutral through spring 2020. On Oct 10, the International Research Institute (IRI) issued an ENSO Quick Look (Fig. 3), emphasizing neutral conditions in oceanic and atmospheric indicators. Their models see ENSO-neutral as the most likely outcome, but remain at “slightly higher chances for El Niño than La Niña”. On Oct 15, the Australian Bureau of Meteorology maintained their ENSO Outlook at ‘inactive’ with most oceanic and atmospheric conditions in the range of neutral. The Oct 2019 North American Multi-Model Ensemble (NMME) saw a turn back towards positive SST anomalies, but is forecast to remain within the range of ENSO-neutral through 2019 (Fig. 4).

 

Summary: ENSO-neutral remains the most likely outcome for 2019 into spring 2020, with oceanic and atmospheric conditions within the range of ENSO-neutral. Seasonal outlooks had been calling for increased chances of above average precipitation and temperatures for late fall and into winter. We originally assumed this was linked to the increased chance of enhanced tropical storm activity in the eastern pacific associated with El Niño, but with a return to ENSO-neutral, El Niño is not a factor. Warmer and (mostly) wetter than normal conditions remain in the seasonal outlooks however (see Fig. 7 on p. 2), although the reason is not entirely clear. November is climatologically relatively dry in the Southwest, so it does not take much precipitation to go above normal, and it may be late season tropical storm activity that is tilting this forecast wet. Tropical storm activity so far has hovered just below average in the eastern Pacific, and in September TS Lorena and TS Mario ushered moisture into the Southwest and interacted with a cutoff low to boost precipitation in southern Arizona (including supercell activity), after a mostly below average monsoon (see Monsoon Tracker on p. 4-6 for details).

 


Online Resources

  • Figure 1 - Australian Bureau of Meteorology - bom.gov.au/climate/enso
  • Figure 2 - NOAA - Climate Prediction Center - cpc.ncep.noaa.gov
  • Figure 3 - International Research Institute for Climate and Society - iri.columbia.edu
  • Figure 4 - NOAA - Climate Prediction Center - cpc.ncep.noaa.gov

Monsoon Recap - October 2019

Wednesday, October 16, 2019

Single weather stations around the region are useful for comparing long term averages to the current year. Figure 1 summarizes monthly precipitation, and shows 2019 lagged behind 2018 and long term averages in most months at most locations. Plots of daily precipitation for stations around the region (Fig. 2) illustrate the slow start and lower than average totals across the region. This monsoon was notable in how much it deviated from the past few years, where many locations in the Southwest saw a run of above normal monsoon precipitation. This made 2019 particularly disappointing. A look at the long term averages demonstrates that 2019 is consistent with some of the drier monsoons on record, even while specific station locations were at or near record driest.

 

Total monsoon precipitation (Fig. 3) varied across the Southwest, with much of the region recording below normal precipitation (Fig. 4), especially in northern Arizona and the four corners. Percent of days with rain (Fig. 5) highlights the regularity of rainfall events, or lack thereof. This was one of the drier monsoons of recent memory, but is consistent with the range of totals in the long term averages. Tropical storms interacting with a cutoff low triggered intense storms in September (Figs. 6-7 on p. 6), and storm locations and tracks are visible on Fig. 4 between Yuma and Phoenix, having boosted otherwise dry conditions.


Online Resources

  • Figures 1-2 - Climate Assessment for the Southwest - climas.arizona.edu
  • Figures 3-7 - Climate Science Applications Program - cals.arizona.edu/climate/misc/SWMonsoonMaps/current/swus_monsoon.html